The present invention relates to a method of recording data, and particularly relates to a method in which video information, namely, a video format signal in the form of a signal timewise divided into blocks and information divided into blocks corresponding to the video information, is recorded in a multiplex manner.
FIG. 1 shows schematically a recorder with which a composite video signal (for brevity hereafter referred to merely as a video signal) having a block structure and another signal divided into blocks are recorded in a multiplex manner employing a conventional method of recording. A video signal from a video signal generator 1 such as a video tape recorder is supplied to a modulator 2 where the video signal is subjected to frequency modulation. At the same time, a digital signal from a digital audio signal generator 3 such as a digital audio tape recorder is supplied to a digital modulator 4. The digital signal from the audio signal generator 3 may be in the form of digital data corresponding to sampled values obtained by sampling an audio signal related to the video signal from the video signal generator 1. The digital data corresponding to the audio signal for a time period corresponding to one field of the video signal constitute one block. The digital modulator 4 modulates the output from the digital audio signal generator 3, adds an error correction code, performs interleaving, etc., employing an EFM (eight-to-fourteen modulation) method.
The output from the modulator 2 and the digital modulator 4 are together by a mixer 5 formed of an addition circuit, etc. The output from the mixer 5 is converted into a rectangular signal by a limiter 6. The rectangular signal is supplied to an E/O (electrooptical) modulator 7. After a light beam from a laser light source 8 is modulated by the E/O modulator 7, the light is diffused by a collimator lens 9 and condensed into a light spot of about 1.mu. in diameter on the recording surface of a matrix disk 11 by a converging lens 10, whereby a layer of photoresist or the like constituting the recording surface is exposed to the light spot. A motor 12 and a servo loop (not shown in the drawings) operate so that the matrix disk 11 is rotated at a prescribed speed and the recording spot advances radially at a rate of about 2.mu. per rotation.
The above-described recorder records the video signal and the digital audio signal on the recording disk in a format as shown in FIGS. 2A and 2B. Among a plurality of blocks formed by dividing the video signal on the basis of a vertical synchronizing signal, blocks corresponding to n-th, (n+1)-th and (n+2)-th fields f.sub.n, f.sub.n+ 1 and f.sub.n+ 2, respectively, are sequentially recorded as shown in FIG. 2A. With reference to FIG. 2B, the n-th, (n+1)-th and (n+2)-th blocks b.sub.n, b.sub.n+ 1 and b.sub.n+ 2 of the digital audio signal, which correspond respectively to the n-th, (n+1)th and (n+2)-th fields f.sub.n, f.sub.n+ 1 and f.sub.n+ 2 of the video signal, are sequentially recorded with a timing independent that of the recording of the video signal. Consequently, the mutually corresponding blocks of the video signal and the digital audio signal are not necessarily recorded in the same position during multiplex recording. As a result, in the conventional method of recording, the video signal and the digital audio signal cannot be reproduced synchronously with regard to the blocks thereof, and hence the video signal and the audio signal relating thereto cannot be reproduced immediately after address search. Therefore, the video signal and the audio signal cannot be efficiently utilized.